Laser drivers find use in the context of hard disk drives and tape storage peripherals, particularly optical disk drives. In general, when information is recorded onto an optical disk using laser light, each recording mark is formed in a disk recording film by a laser pulse train thereby to perform information recording. The laser pulse train used at this time is called “recording strategy”.
Information about the recording strategy comprises power levels (hereinafter defined as “power levels”) of laser pulses and their pulse light-emitting timings (hereinafter defined as “pulse timings”). It is necessary to optimize these parameters according to recording conditions such as the type of optical disk, the length of each recording mark and the length of space defined therebetween, a recoding speed, etc.
In an optical disk apparatus, a laser is driven using a laser drive circuit (hereinafter described as “laser driver”) mounted onto a pickup based on recording strategy information thereby to generate laser pulses.
In general, laser driver requirements for disk drives require two different current levels to operate properly. The first is a pulse or active level that turns the laser sufficiently on to reduce the coercivity of the magnetic media (through heating) to a point where writers can flip the magnetic polarity. The second is a threshold level, which is lower than the pulse level and just below the lasing point where the media is not heated, but high enough for a fast transition back to the pulse lasing level.